Orthokon is played on a 4×4 board with the following setup:
Players take turn to a as far as it can go in any of the 8 directions. It is not allowed to stop halfway.
After moving, all orthogonally adjacent pieces become the colour of the current player.
Here Player 2 opts to b1 to d3, taking over both c3 and d2 !
A good reply for Player 1 would be c1 to c2.
You win if your opponent has no valid move on their next turn.